Gas turbine engines include one or more combustors adapted to produce a hot gas by burning a fuel in compressed air. A fuel injecting assembly or nozzle is employed to introduce the fuel into each combustor. To provide flexibility to the user, such fuel nozzles are often of the dual fuel type that are capable of burning either a liquid or a gaseous fuel, or both simultaneously.
Combustion in gas turbine combustors results in the formation of oxides of nitrogen (NOx) in the combusted gas, which is considered undesirable. One method of minimizing the formation of NOx involves injecting steam, via the fuel injecting nozzle, into the combustor along with the fuel.
U.S. Pat. No. 5,361,578 discloses a fuel nozzle assembly capable of burning either gaseous or liquid fuel, or both, along with steam injection. The fuel nozzle assembly includes an expansion bellows in an inner sleeve and an expansion bellows in a middle sleeve so as to reduce stresses in the inner and middle sleeves due to thermal expansion. While accommodating differential expansion between portions of the fuel nozzle assembly, bellows between the circumferential chambers have a limited life.